The statistical mechanics of condensing systems

Abstract J. E. Mayer (1937) has published, together with some collaborators, several papers under the same title as the present one. We consider these papers as a most important contribution to statistical mechanics, and this opinion was shared by the International Conference held in Amsterdam, 26 November 1937, in commemoration of Van der Waals’ birth. One of the present authors gave to this meeting a report on Mayer’s work (published in Physica, 1937) which was followed by a vigorous dis­cussion on the question as to whether Mayer’s explanation of the pheno­mena of condensation is correct. Doubts about this point were raised by the referee, because it is difficult to comprehend how a method of approxi­mation such as that of Mayer, starting from the gaseous state, can lead to the discontinuity of the density on an isothermal curve which corresponds to condensation. The usual methods for treating the equilibrium of two phases introduce the equation of state of both phases and derive the con­dition for their co-existence. Mayer’s theory does nothing of this kind, but treats all possible molecular arrangements with their proper weight, as if there were only one phase. How can the gas molecules “know” when they have to coagulate to form a liquid or solid? Mayer’s mathematical method is too involved to make this point quite clear.